Rock & Mineral Encyclopedia

Search and identify 1,000+ rocks, minerals, crystals, and gemstones — with properties, formation, colors, hardness, and how to tell them apart.

Asphalt Rock

A porous sedimentary rock naturally saturated with bitumen, dark, tarry-smelling, and historically mined for paving.

A man-made glittering glass packed with tiny copper crystals, traditionally reddish-brown but also made in blue and green.

A man-made glittering glass colored deep blue with cobalt and studded with tiny copper crystals that mimic a starry night sky.

A rare boron-bearing feldspar, the boron analogue of albite, first found in oil-shale nodules of the Green River Formation.

The magnesium-rich brown member of the tourmaline group, named for Austria's Drava River and prized for warm earthy tones.

A coarse sedimentary rock of rounded pebbles and gravel cemented in a finer matrix, recording ancient rivers and beaches.

A fine-grained clastic rock of silt-sized grains, intermediate between sandstone and mudstone, with a gritty feel.

A royal-blue feldspathoid mineral with white calcite veining, often confused with lapis lazuli but lacking its golden pyrite flecks.

A rare platinum arsenide and the most important platinum-bearing mineral, forming bright metallic cubic crystals.

Extremely fine-grained, even-textured limestone famous for lithographic printing and for preserving exquisite fossils like Archaeopteryx.

A metallic cobalt-nickel arsenide, an important cobalt ore, named for the Skutterud mines of Norway.

A silver sulfide that is one of the most important silver ore minerals, forming dark metallic crystals and wires.

A soft pink to crimson hydrated cobalt arsenate, famous as cobalt bloom that signals nearby cobalt ores.

A pale copper-red nickel arsenide, historically called kupfernickel, that is an ore of nickel and gives the metal its name.